1. Field of the Invention
The present invention relates to a message synthesizer circuit, and more particularly to a synthesizer circuit which can generate a desired tone or voice message.
2. Prior Art
As shown in FIG. 1, in a conventional message synthesizer circuit, a melody, for example, an eight-bit data representation for a single tone of the piano, is turned into compressed PCM data to store into a memory 11, which serves as a message source, and the PCM data is sequentially read out to reproduce the melody by means of a PCM decoder 12. While for speech, a single message such as "Ohayou (Good morning)" is similarly compressed into ADPCM (Adaptive Differential Pulse Code Modulation) or DPCM (Differential Pulse Code Modulation) data to store into a compressed message data memory 11, which serves as the message source. In this case, the basic bit processing systems are the same, whether a single message frame such as "Ohayou" be stored as a single block of data, or "o", "ha", "yo" and "u" be each stored as the unit tone. Incidentally, in the case of a PARCOR (Partial Autocorrelation) system, a specific PARCOR data processing is used. However, in either case, the compressed message data memory 11 is provided as the message source for storing the compressed message data.
In operation of the conventional message sysnthesizer circuit, a message code signal 109 for specifying a message is entered, and a start signal 110 is entered to latch the message code signal by a latch circuit 9, and then the compressed message data specified by the message code signal 109 is read out from the specified address of the compressed message data memory 11 by a system controller 10. The compressed message data which has been read out is expanded and decoded by a compressed message data decoder (PCM decoder) 12 and, after conversion into an analog signal by a D/A (digital-to-analog) converter 13, it is passed through a message demodulating filter or a low pass filter 14 to emit a synthesized message for obtaining a specific message.
In some applications (for example, a toy and the like) of the above-described conventional message synthesizer circuit, variations such as "Ohayou", "Kon-nichiwa (Hello)" or "Konbanwa (Good evening)" are often needed as casual and random message data outputs rather than "Ohayou", which is the stereotyped message data.
However, in the above-described conventional message synthesizer circuit, in order to achieve any random message output, it is necessary to enter a corresponding message code signal from the exterior and, accordingly, for that purpose, an external circuit becomes necessary.